Telephone system



Mardl 40- w.'-|-|. T. HOLYDEN 2,195,309

TELEPHONE SYSTEM Filed Feb. 24, 1939 T0 CHAIN CIRCUIT g? WWW ill I\ ll illlHl TO CONN.

MULT.

/N l/E N TOR m 7.'HQLDN GPM ATTORNEY Patented Mari26, 194() l I.

UNITED sr'lss PATENT oFF cE-JI I TELEPHONE SYSTEM William 'r. Holden, Long Island city, N. Y., as-

signorto Bell Telephone Laboratories, Incorporatcd, New York, N. Y., a corporation of'New H Applioation February 24, 1939,:Serial No. 258,129

6 Claims. 7 (Cl. 179 -18) This invention relates to telephone systems and calling line. This arrangement overcomes [the particularly to an improvement in the system I possibility, present in othersystems of thiskind, disclosed in the copending application of William. of the second line stealing the first assigned line H. Martin, Ser. No. 258,133, filed Feb. 24, 1939. finder without itself having the power to produce .1 The object of the invention is to eliminate some a sufliciently strong impulse to fire the second 5 of the individual equipment usually provided for tube and thereby initiatethe operation of-another subscribers lines, especially the :line and cut-off line-finder switch. t v relays. I v The foregoing and'other features of the inven- It has been proposed heretoforeto eliminate tion will bedescribed in detail in the following the individual line relays'an'd to replace them by specification, which'should be read in. conjunc a relay mechanism common toa group of lines t on With the a t tfi drawing e p ny To accomplish this, however, it would be necesing claims. L i s sary to provide an auxiliary switching mecha- The drawing represents, schematically, a-t ele- 1 nism for associating tl' excommon relay mechaphone system in which the features of theinvennism with any one of the lines when calling. tion are embodied in a circuit structureithat 5 It has also been proposed to use a Vacuum tube makes -S of au Switches, of th W -in common to a group of lines, the control elek own two-motio step-byp yp It i u ment of which is connected'through individual derstood, however, that the embodiment of the resistances to the respective subscribers? lines, invention as-helifl Set forth is E by w y of, thus doing away with the individual line relays, i ust ation only, n t the invention m ybe 20 and toutilize the vacuum tube as thesignaling y pp nyo h p of autflmatifi means for starting the line-finder switch that semiautomatic telephone S m- I t is to be used for connecting with the terminals Referring t the drawing, there a e Shown tWO of the calling line. Anarrangement of this kind, subscriber s a vof a r p o twe ty s,

however, is subject to falseoperation due to the statiensA n D i h up, a lin i 25 combined efiect of several line leaks, and'further cuit LC associated with station A, a; linefinder does not lend itself readily 'toa line terminal'test Switch LFtWSBIBCtOIF Switch 5, connector Switch which is sufficiently positive and reliable to enable d t a d su r e s stati the line finder to distinguish and seize the par The'subscribersstatims A B and D re p ticular calling line in'the group that is calling, Vided W th t e usua subscribers set which is especially Wherea plur lit 1 li ithi th equipped with a dial forcontrolling the establishsame calling group initiate c ll in th int mentof thedesired connections. The selector between the origination of the first call by a; line w c S a he connector Switch C are of t and the connection thereof to a line-finder switch Well-known P- Y- l 1, Strowger. typ and th ith, i i 1 reference may be had to pages 53 to 67, inclusive,

According to the presentinvention, these clifof the s c edition'of Automat p y ficulties are overcome-by the use of three gaseous y Smith and Campbell 5 iled e pconductor tube devices having single control election of the operation of the circuits associated:

trodes two of which are inductively coupled to the With these switches, 'On y those P01110115 Of 40 group of lines to produce an impulse when a line circuits of the selector and connector switches 40 calls that will alter the potential of one of the are shown as are'requiredfor a clear and comcontrol electrodesso as to render the associated plete description of this invention, the omitted tube conducting and thereby establishan anode portions vof these circuits being indicated by cathode circuit theret'hrough which, in'turn; will broken lines. i I 1 ,5 initiate the'operation ofa line-finder switch that The line circuit LC and the line-finder switch willhunt for the test terlninal of the calling line. LF are: shown in detail since the features of the Another feature Of the invention is a circuit invention apply 'spe cifically to these circuits, arran m e th p in Potential Q Three cold cathode gaseous discharge tubes T1,-T2, the space current of the tube, made conducting by T are associated in common with a groupof line the initiation of a call by'one line, is used to rcncircuits such as those associatedw'ith the group of 50 der the control electrode of the succeeding tube stationsA D, forexample, the control elec critical to the slightly weaker impulse produced 'tIOdG 4 of tube T l'and the control electrode ,3 by a second line in the group initiating a call of tube T2 being/connected in parallel to ,the before the line-finder switch started by the flrst secondary winding S of transformer 9 through tube has reached the test terminal of the first condensers 6 and i8 and current limiting resist- 55 tentials of their associated cathodes. Each individual line circuit .ofthe group, such as line circuit LC, connects with the primary side P of transformer 9 over one line conductor through individual resistances such as, for instance, resistances 42 and 4| for subscribers line A. The mid-(point connection between the two resistances is connected to the test terminal 23 of the line in thebank of terminals accessible to the linefinder switches, such as switch LF.

As already stated, the control electrode 3 of the second tube T2 is further connected to the secondary S of transformer 9 by way of series condenser l8 and its associated resistance while'the cathode 5 of the first tube T1 is connected .directly to the segment on the commutator which designates the horizontal level of the line group controlled by the tubes T1, T2 and Tsfan'd through resistance 3'! to the winding of relay l2 via the No. 4 normal contacts of relay 33 in the preferred line finderLF, and alsoto the control electrode 3 of tube T2 through resistance 3, to the con- .trolelectrode M of tube T3 through condenser 29 and resistance 28, and to the source of positive power supply 24 through condenser 29 and resist ance 21. V V

Each line circuit connects to a set of three terminals appearing in the terminal banks accessible to a group of line-finder switches, as indicated by the individual line circuit LC which connects to terminals 2 I, 22 and 23. The line-finder switch LP is of the well-known step-by-step type providecl with two banks each of one hundred sets of terminals of which the upper bank of one hundred terminals is typically represented by the ter- I minals 2!, 22 and 23 and the lower bank of one hundred terminals by terminals 3 I, 32 and 33, said lastgroup of terminals being located in a level corresponding to the level which holds the first group. The two banks of terminal sets are arranged in ten levels, each level consisting of ten horizontal terminal sets, the upper bank sets being selectable by brushes I5, I 5, H and the lower bank sets by [5, l 6' and H. These brushes, as well as brush 8, are carried on a common shaft (not shown) which is advanced vertically to the proper lever and then horizontally .to the terminals of the calling line under control of the vertical magnet I l for vertical stepping and the rotary magnet 22 for horizontal stepping, respectively. The line finder is provided with a vertical commu tator 1 which has ten conducting segments, one for each two levels of terminals in similar horizontal disposition in eachof the two terminal banks. Associated with. this commutator is a brush 3 which, as stated before, is mounted on the common brush shaft'and advances simultaneously with brushes [5" to- H, inclusive, and I5 toll, inclusive, during vertical stepping to engage the successive segments of the commutator.

The operations of the circuits controlling the setting of a connection will now be fully set forth in detail in the following description of a callini-.

tiated from station A for termination at sta- .tion B.

When the receiver is removed from the switch- .with through resistances 34 and Hi to negative battery 35. Control electrode 4 of tube T1 is normally at a positive bias. This is because the potentiometer resistances 35,. 34 and ID are so calculated as to place a critical positive potential on electrode .4 but not sufficient to fire the tube unless a positive impulse is produced through the transformer 9 or tube T3 is conducting as will be explained later. Control electrode 3 of tube T2, on the other hand, has no bias of any kind since its control electrode 3 is connected, through resistance l3, to the cathode battery of tube T1, and will not be able to fire unless such electrode is rendered positive. Hence when the impulse is produced through the transformer, the potential of electrode 4 is raised to the flash point of the tube, causing it to break down between control electrode 4 and cathode 5, afterwhich a current is established between cathode '5 and anode l9, over the following path: positive battery 24, anode l9, cathode 5, resistance 31, conductor 55, No. 4 normal contacts of relay .38, winding of relay l2, No. 3 contacts of relay 39 to negative battery. Relay l2 operates and performs functions noted hereinafter. The full potential drop in resistance 31 and relay winding I2 is further applied to terminal 8 of the vertical marking commutator 1, thus indicating that the calling line is in the group of lines located on the eighth level of terminals either in the upper set or lower bank of terminals. i

It will be observed that the inductive surge through transformer 9 is also applied to the control electrode 3 of tube T2 but that this electrode has no positive bias as in the'case of the control electrode of tube T1. Hence the positive potential created by the surge will not be sufiicient to render the control electrode positive enough to cause tube T2 to breakdown. However, when tube T1 has broken down in the manner already described, the potential drop in the resistance 31 and relay Winding l 2 is available as a positive bias voltage between the control electrode 3 and cathode 60 of tube T2, through resistance l3.. That is to say, tube T2 now has acquired a positive bias on its control electrode 3 so that a second impulse produced through the transformer 9 will have the effect of rendering control electrode 3 sufficiently positive to cause tube T2 to break down and perform functions hereinafter described.

Assumethat terminals 2|, 22 and 23, associated with the line circuit LC of calling station A, are the fifth set of terminals in the eighth level of the upper bank of terminals of the line-finder switch. Tubes T1, T2 and T3 are common to all of the twenty lines appearing in the eighth level of each of the two terminal banks, each of these of commutator -1 and relay .IZ is operated aspreviously described. Relay l2 grounds the, sleeve lead 44 to the selector S atitsupper inner contacts, and closes a circuit for relay extending from ground on the No. 3 contacts of relay I2, contacts of vertical magnet II, contacts of rotary magnet 20, lower winding ofrelay 45, to battery on the No. 3 contacts of relay 38. Relay 45 operatesand closes the circuit of vertical magnet i from battery on the No. 3 contacts of relay 38, winding of vertical magnet H, No. 4 back contacts of relay 46, contacts of relay '45 to ground on'the lower contacts of relay i2. I Vertical magnet I l operates and lifts the brush shaft one vertical step to the first level otterminals and breaks its own contacts to release relay 45 k by the presence of the potential from cathode- 5 of tube T1 on the eighth segment of the com mutator 7. When this segment is reached, a circuit is completed for relay 45 in series with lower winding of relay 65, which circuit extends from positive battery 24, anode I9 and cathode 5 of tube T1, eighth commutator segment, brush 8, upper winding of relay 45, outer contacts of rotary magnet 25, lower. winding of relay $5, No;

3 contacts of relay 38, to negative battery. Relay lfi operates, looks over its lower winding to ground on the contacts of relay l2, and further holds relay45 operated to prevent further .vertical stepping. Relay lfi transfers the locking circuit of relay 41 from the off-normal ground on the vertical ofi-normal contacts VON, which operates on the first vertical step of thebrush shaft, to acircuit path which is partially comof vibration. Relay 45 also transfers the stepping circuit from the vertical magnetll to the rotary magnet 29 over the following path: battery through the winding of rotary magnet 25,

No. 4 front contacts of relay 45, contacts of relay 45 to groundon the lower contacts of relay H2. The rotary magnet 20 now steps thebrush shaft around on the eighthlevel terminals (causing thereby the disengagement ofbrush 8 from the eighth commutator segment), and, onthe first step, efiects a release of relay 55 because over the previously traced circuit, in turn caus-' ingthe operation of rotary magnet 20 to effect a the disengagementof brush& with the eighth segment of commutator i and opens the previously traced holding circuit through the operating winding of relay 45. Relay 45 now reoperates It will be observed that two othergaseous con ductor tubes 3-! and F--! are provided, the anodes of which are paralleled to the positive direct current superimposed upon the source of alternating current 48, while the control electrode 49 of tube B-l is connected to the upper test brush ll throughcurrent limiting resistance 53 and the control electrode 56 of tube F-l is connected to the lower test brush ll" through current limiting resistance 54.-. The cathodes. 5!

and 52, respectively, of both tubes are kept at ground potential so that neither tube is in a conducting state so long as its control electrode is not rendered positive during the positive halfe cycle of the alternator 18. However, when test brush i'l engages terminal 23 of the calling line A, the positive potential on this terminal is applied to control electrode 49 of tube B--l via resistance 53. Since cathode 51 is at ground-potential, the potential difierence between cathode 4Q and control electrode 5| will cause tube B-l 'to break down and become conducting between its anode'and cathode as soon as the alternator 48 reaches the positive half-cycle after the electrode 49 has been rendered positive.

. If the calling line A had been located in the eighth terminal level at the lower bank, as for instance line D, the line positive potential would have been impressed upon terminall33 with which brush ll would have been engaged, whereupon tween control electrode 55 andcathode 52 would cause tube Bl to breakdown and become conducting.

Assuming, however, that the calling line is line 1 A, located in the upper bank, then the engage ment of brush ll with terminal 23 results in tube E ibecoming conducting, whereupon a circuit is'completed for relay ll in series with the upper winding of relay 55, extending from posi tive potential at cathode 5!, lower winding of relay ill, Not 5 back contacts of relay 39, No. 5 normal contacts of relay 41, upper winding of relay 45 to ground on the No. 2 contacts of re lay [2; Relay il operates, at leastto the extent of closing its No." 2 contacts.

Since relay this operated and rotary magnet Zll is held through the No. 4 front contacts of said relay tov ground on the lower contacts of relay [2 via the contacts of relay. dd, the full operatingand loclcing circuit of relay ll is completed over the inner contacts of rotary magnet Lid, contacts of relay 45 to ground on the lower contacts of relay Hi. It is necessary to insure a fast auxiliary circuit'to completely en ergize relay 4? because when alternator it reaches the negativehalf-cycle, the anode of tube B-l becomes negative and the tube extin gui shes, thereby opening the initial operating circuitotrelay 4'5. A circuit is now completed for relay 39, extending from battery throughim lower winding, No. 3 contacts of rel il, inner contacts of magnet, 26, contacts of relay %5 to ground on the lower contacts of relay l2.

Note that if line D had initiated call instead of line A, the-calling potential would be present, of course, on terminal instead or terminal 23 and tube F-i would have been ren dered conducting instead of tube Bl. Under these assumed circumstances, relay ll would not operate but. relay 39 would in a circuit completed from the positive potential availableat cathode 7 52, upper winding'of relay 39, No. 1 back contacts of relay 38, upper winding of relay 45 to ground on the No. 2 contacts of relay [2. Relay 39, upon operating, would then lock over its lower winding through the circuit path already described.

The operation of relay 39 extends the talking conductors from the No. 1 and No. 4 front contacts of relay 41, over its ownNo. 1 and No. 6 contacts, respectively, to the selector S, opens the initial circuit of relay 4'! at its No. 5 back contacts, closes a circuit for relay 38 which extends from battery through its upper winding,

The operation of relay 38 joins sleeve brush ll of the line finder LP to sleeve conductor Moi the selector S over the No. 1 front contacts of said relay and the No. 5 alternate contacts of relay 41, extends the locking ground of relay 39 to said conductor 44 over its No. 2 contacts, advances the starting conductor 55 to relay I2 in the next succeeding idle line-finder switch in the chain over its No. 4 contacts, and removes battery from relays 45 and 46 and vertical magnet ll. Relay 38 further connects alternating potential source 5! battery to conductor 55 which connects with the cathode 5 of tube T1. Since the effect of this is to connect negative potential to the cathode 5 on every half-cycle of the alternator 51, then on the positive portion of the wave, cathode 5 is rendered positive. Should another line in the group now initiate a call, tube T1 will break down by virtueof exactly identical circuit conditions established through relay !2 of the succeeding line finder by the operation of relay 38. However, while the succeeding line finder is hunting for the calling line, the tube T1 will remain conducting because of the cathode-anode circuit heretofore described but now through the winding of relay 12 of the succeeding line finder. There will be, in addition, a flow of pulsating current from the superimposed source 5! through the I, lower winding of relay 38 which will prevent this relay from releasing while relay I2 in the succeeding line finder is operated. However, when the circuit through relay I2 is opened in the succeeding line finder as described for the line finder shown in the drawing, pulsating current will continue to flow through both relays 38 to the cathode 5 of tube T1 which will then become nonconducting in the negative half-cycle afterrelay l2 in the succeeding line finder has released.

The calling line A is now extended to the first selector S which is then positioned on the terminals of an appropriate connector C by one series of dial impulses, the connector itself being then positioned on the terminals of the called station B by the next two series of dial impulses transmitted from the dial at station A, all in accordance with well-known automatic telephone practice. Since this part of the operation as well as the release of the connection forms no part of this invention, further description thereof is omitted.

superimposed on negative tube T1 and the cathode 65 of tube T3.

If a second line in the group of twenty lines attempts to initiate a call after a previous line has caused tube T1 to become conducting but before the line-finder operations above described have been completed, the second positive impulse from the surge through transformer 9 will cause tube T2 to break down and become conduct-ing because of the presence of the positive bias on the control electrode 3 of tube T2 as previously described. Note that unless tube T1 is conducting, the surge voltage from transformerB will not cause tube T2 to break down. Tube T2 is maintained conducting over a cathode-anode circuit extending from positive battery 24, anode El and cathode 6U, resistance 2 to negative battery 35. The potential drop in resistance 2 applies a critical positive bias to control electrode M of tube T3 via resistance 62 and resistance 28. Now when tube T1 becomes non-conducting as a result of the operation of relay 39, a positive inductive surge from the winding of relay l2 and that inherent in the internal inductance of tube T1 will be applied to the control anode M of tube T3 via condenser 29 and resistance 28 causing said tube to break down and become conducting. Tube T2' is now extinguished by the positive surge applied to its cathode 69 through the commutating condenser 59. But when tube T3 is conducting, the potentiometer formed by resistances 34 and 35 together with the voltage drop in resistance Ill applies 'a positive voltage to the control electrode 4 of tube T1. This voltage, however, is not applied immediately, but only after a delay as required by. the charging time of condenser 58 through resistance 34. This delay is introduced to allow time for the operation of relay 38 after the operation of relay 39. The potential thus applied to control electrode 4 oitube T1 will cause it tobreak down again to initiate the operation of the next succeeding line finder via conductors 55 and 56. When tube T1 thus reoperates it extinguishes the discharge in tube T3 by means of the commutating condenser 64 connected between the cathode 5 of The circuit is now in the same condition as that existing just after a single subscriber such as A has initiated a call and the operations are the same as those'described.

While this embodiment of the invention has been described with reference to a line-finder system in which there are three tubes to accommodate the satisfactory initiating of two overlapping calls in the same group of lines, it is evident that the tube counting circuit could be adapted to store as many overlapping calls as might be required by the provision of addione. of said devices operative to effect a connection of one of said connecting means to said calling line and renders critical a succeeding one of said devices through said network to the inductive surge following the initiation of another call from another of said lines before said connecting means eifeots a juncture with said calling line.

2. In a telephone system, the combination interconnecting said devices.

with a group of lines and connecting means therefor of a first starting gaseous conductor device inductively connected to said group of lines and operatively associated with said connecting means, a group of call-storing gaseous conductor of a precedingdevice, whereby the initiation of a call by one of said lines produces an inductive surge that renderssaid first startingdevice conductive to effect a juncture of said connecting means with said calling line subsequent to which said starting device is reset by the disrupture of its operative. association with said'connecting 1 means, whereby a plurality of succeeding calls initiated before said juncture is affected are recorded in succession on each of said call-storing devices by being rendered conductive, respectively, in response to inductive surges, and whereby said second starting device is rendered conducting by the resetting of said first starting device and saidfirst starting device is rendered conducting by the conductive surge produced through said network. v

3. In a telephone system, a group'of lines disposed upon the terminals of a line-finder bank, a line-finder'switch adapted to hunt thereover, a gaseous conductor starting device for said line finder inductively coupled to said group of lines line prior to said line finder reaching theter minals of the line which initiated the first'call, and another gaseous conductor starting device for rendering said first gaseous conductor starting device conductive after being reset by said line-finder switch, said three gaseous conductor devices being disposed in relation to each other to be rendered critically responsive, in succession, by the conductive condition of a preceding device.

4. In a telephone system, a group oflines disposed upon the terminals of a line-finder bank,

a line-finder switch adapted to hunt thereover, a gaseous conductor starting device for said line finder inductively coupled to said group of lines and adapted to be rendered conducting by the inductive surge produced when one of said lines calls for operating said line finder to hunt for the terminals of the calling line, and a group of gaseous conductor storage devices for storing successive calls initiated prior to said line finder reaching the terminals of said line, said storage devices being inductively coupled to said group of lines and rendered conducting in succession through surges. created by other calling lines, said storage devices being adapted in relation to each other and to said starting device to be rendered. critically responsive in succession by the conductive condition of a preceding device.

succession, critically responsive by the conducting state of a preceding device, whereby the initiation of a call by one of said lines produces an inductive surge that renders said starting device c'onductingto effect a connection of said connecting means with said calling line and whereby the initiation of aplurality of successive calls, thereafter but before said connecting means is joined tosaid calling line, produces a succession of inductive surges that renders successivestorage devices conducting to store each of said calls.

6( In a telephone system, the combination with a group of lines and connecting means therefor of a gaseous conductor starting device and a" group of gaseous conductor storage devices all inductively coupled to said group of lines whereby the initiationof a call by aline in the group produces, an, inductive surge that renderssaid starting device conductive'to effect a connection of said connecting means to said calling line and whereby theinitiation of other calls from other lines in the group before said connecting means effects a connection with said line produces corresponding inductive surges which render eachof said storage devices conductive to record the initiation of-a call.

WILLIAM H. T. HOLDEN. 

